Nutrition and Iron Absorption Quiz

Iron Absorption

• Daily requirement: 0.6 mg
• Absorption: upper part of small intestine
• Storage: in the liver
• Functions: formation of Hb and myoglobin
• Requires: HCl and vitamin C
• Deficiency: microcytic anemia
• Iron in diet is ferric
• Reduction of ferric to ferrous occurs by gastric HCl and ascorbic acid (vitamin C)
• Iron absorbed mainly in the upper part of the small intestine (duodenum)
• Part of iron is delivered to mitochondria
• Remaining part is either combined with apoferritin (in intestine) or carried in plasma on transferrin
• Iron combined with apoferritin is changed to ferritin, the main storage of iron
• Iron is transported in blood bound to transferrin to all parts of the body and stored in the liver as ferritin
• Deficiency in iron is due to:
  • Decreased intake
  • Decreased absorption
  • Chronic blood loss (e.g., piles)

B12 Absorption

• Daily requirement: 5 µg
• Absorption: lower part of small intestine (terminal ileum)
• Storage: in the liver
• Functions: DNA formation, cell division, cell maturation, and formation of myelin sheath
• Requires: intrinsic factor
• Deficiency: macrocytic anemia
• Intrinsic factor is secreted by the gastric gland (parietal cell)
• Intrinsic factor combines with vitamin B12 for protection and transport
• Vitamin B12 is absorbed from the lower part of the small intestine (ileum)
• Vitamin B12 enters mucosal cells with intrinsic factor by pinocytosis
• Inside the cell, vitamin B12 is released to be absorbed into the blood, where it binds to transcobalamin II
• Transported to all parts of the body and stored in the liver
• Deficiency in vitamin B12 may be due to:
  • Decreased intake (rare)
  • Decreased absorption

Anemias

• Pathological conditions characterized by a decreased number of red blood cells (RBCs) or hemoglobin (Hb) content
• Classification:
  • Etiological (cause):
    • Precursor cell failure:
      • Iron deficiency
      • Vitamin B12 deficiency (megaloblastic)
      • Anemia of renal disease
      • Anemia of endocrine disease (pituitary, adrenal, and thyroid hormone deficiency)
    • Hemorrhagic anemia (blood loss):
      • Acute blood loss (accidents, hematemesis)
      • Chronic blood loss (piles)
    • Hemolytic anemia (RBC destruction):
      • Extracorpuscular causes (acquired):
        • Chemicals (e.g., lead poisoning)
        • Diseases (e.g., malaria)
        • Snake venom
        • Severe trauma
        • Hypersplenism
        • Incompatible transfusion
      • Intracorpuscular causes (congenital):
        • Abnormal RBCs (e.g., spherocytosis)
        • Congenital deficiency of G6PD enzyme
        • Abnormal hemoglobin (e.g., sickle cell anemia)
    • Stem cell failure (aplastic anemia): bone marrow damage
      • Irradiation (gamma rays)
      • Drugs (e.g., chloramphenicol)
      • Chemicals (e.g., arsenic)
      • Leukemia
      • Chronic bone infections
  • Nutritional/deficiency anemia
  • Morphological (RBC size):
    • Normocytic normochromic anemia
      • Acute hemorrhage
      • Hemolytic anemia
      • Bone marrow failure
      • Chronic diseases
    • Microcytic hypochromic anemia: iron deficiency anemia
    • Macrocytic anemia: vitamin B12 and folic acid deficiency

Effects of Anemia

• Pallor (seen in mucous membrane and nail bed)
• General ill health (rapid fatigue and dyspnea)
• Headache, blurred vision, and fainting
• Tachycardia and increased pulse pressure
• Specific signs:
  • Iron deficiency: spooning of the nails
  • Hemolytic anemia: jaundice
  • Sickle cell anemia: leg ulcers
  • Megaloblastic anemia: sensory disturbances

Pernicious Anemia

• Autoimmune familial disease, more common in elderly
• Due to an immune reaction against parietal cells, causing achlorhydria and absence of intrinsic factor
• Degeneration of the posterior and lateral columns of the spinal cord leading to neurological manifestations

Treatment of Anemia

• Treat the underlying cause:
  • Iron deficiency: iron supplementation (oral or injection)
  • Pernicious anemia: vitamin B12 injection
  • Folic acid deficiency: folic acid
• Severe cases: blood transfusion

Blood Indices

• Values obtained relating hemoglobin (Hb), packed cell volume (PCV or hematocrit), and red blood cell (RBC) count
• Color index (CI): rough indication of Hb content compared to normal
  • CI = Hb content (% of normal) / RBC count (% of normal)
  • Normal CI: 0.9-1.1
  • High in pernicious anemia, low in iron deficiency
• Mean corpuscular volume (MCV): hematocrit x 10 / RBC count
• Mean corpuscular hemoglobin (MCH): Hb/100 mL blood / RBC count
• Mean corpuscular hemoglobin concentration (MCHC): Hb/100 mL blood / hematocrit

Test your knowledge on the essential nutrients in human nutrition, focusing on iron and vitamin B12. This quiz covers key concepts like absorption sites, storage forms, and anemia types. Perfect for those studying human biology or nutrition.